Consumers also aren't advised to carrying balances on cards with lower interest rates rather than those with high rates. ASIC estimates these consumers could have saved about $621 million in interest in the past financial year if they had carried a balance on a card with a lower interest rate.

"Only a handful of credit providers take proactive steps to address persistent debt, low repayments or poorly suited products. There are a number of failures by lenders to act in the interests of consumers," Mr Kell said.

With balance transfers, many consumers reduce their credit card debt during the promotional period, but more than 30 per cent of them increase their debt by 10 per cent after transferring a balance.

Four lenders (Citi, Latitude, American Express and Macquarie) have retained old rules for grandfathered credit cards open before June 2012, when ASIC introduced rules that required lenders to apply repayments against the cards that have the highest interest rate.

While these four credit providers are not breaking the law, they are charging their longstanding customers more interest than they should have been.

SNAPSHOT OF THE REVIEW:

- 14 million open credit card accounts, an increase of over 300,000 since 2012

- Outstanding balances totalled almost $45 billion

- About $31.7 billion in balances on credit cards that are incurring interest charges

- Consumers charged about $1.5 billion in fees in 2016-17, including annual fees, late payment fees and other amounts for credit card use

- Around 62 per cent of consumers had only one credit card between 2012 and 2017

- Consumers with multiple cards generally had two cards

- Fewer than 5 per cent of consumers had five or more credit cards between 2012 and 2017.